1. Field of the Invention
The present invention concerns a method of manufacturing a clutch cover assembly of the kind comprising a pre-assembled combination of an axially fixed part, namely a cover, and a part, namely a pressure plate, which is axially movable under the action of elastic means, means being provided for limiting axial movement of the axially movable part.
The present invention also concerns a clutch cover assembly manufactured by this method.
The invention is more particularly, but not exclusively, concerned with a method of manufacturing a clutch cover assembly in which the means for limiting axial movement of the pressure plate are also adapted to limit radial movement of this plate when the assembly is pre-assembled and stored.
2. Description of the Prior Art
French Patent Application No. 82 10785 describes means for limiting axial and radial movement of the pressure plate. It is known that, following an impact to the edge of the pre-assembled clutch cover assembly in the storage position, caused by dropping it, for example, the pressure plate is acted on by axial and radial forces causing deformation of at least two of the driving straps of the pressure plate, one in bending and the other in buckling.
It is also known that in certain assemblies in the storage position the driving straps are stressed to their maximum elasticity. Deformation in buckling through a few hundredths of a millimeter can thus be prejudicial to their return force properties.
In other kinds of clutch cover assembly, however, it is not necessary to so strictly limit radial movement of the pressure plate and in such cases means for limiting the radial travel of said plate, such as those described in the French patent application mentioned hereinabove, are not needed although, on the other hand, means for limiting axial movement are indispensable to avoiding deformation through a few tenths of a millimeter consequent upon axial movement of the pressure plate.
The implementation of means for limiting either axial movement only or axial and radial movement of the pressure plate may give rise to a number of disadvantages during the assembly of the clutch cover assembly.
Firstly, it must be remembered that the means for limiting axial movement of the pressure plate already known in the prior art are more often than not in the form of a pin attached either to the pressure plate or to the cover and sliding in a hole in the other of these two parts. These pins comprise a cylindrical shoulder the diameter of which is substantially greater than that of the hole, so that this shoulder cooperates with the hole to limit axial movement of the pressure plate.
In the French patent application mentioned hereinabove, it is proposed to provide these pins with a frustoconical shoulder adapted to permit immobilization of the pressure plate in the radial direction in the storage position.
This solution gives satisfaction in many cases, but there nevertheless remain a number of clutch cover assemblies in which it may not be adopted.
There are cases in which such pins cannot be used, whether comprising a cylindrical or a frustoconical shoulder.
The assignees of the present applicants have filed other patent applications covering other means of limiting axial movement of the pressure plate. In the application mentioned hereinabove, the means proposed include cups and a limiting member comprising a limiting arm carried either by the pressure plate or by the cover and cooperating with an edge on the second of the two parts. This solution gives satisfaction in certain cases where pins may not be used.
Nevertheless, there remain a number of cases in which this solution, as disclosed in the application mentioned hereinabove, cannot give complete satisfaction. This is the case, for example, when it is not possible to insert a bulky limiting part into a corresponding opening, the limiting part already having its final shape. It is also the case when the manufacturing tolerances for the various parts of the clutch cover assembly are such that, in order to avoid radial movement of the order of a few hundredths of a millimeter, it would in practice be necessary to provide a part or a member to limit radial movement adapted to each individual clutch cover assembly produced.